The present invention is particularly important in its application to the preparation of biologically active compounds comprising the cyclic peroxyacetal lactone or lactol functionalities.
One such biologically active compound is qinghaosu (Artemisinin) which has the following formula: ##STR1##
Qinghaosu is a potent antimalarial which has been successfully used to treat patients suffering from malaria. The reemergence of strains of malaria resistant to conventional (chloroquine) therapy is posing a worldwide problem, and indeed, there is no universally acceptable cure at the present time. Qinghaosu occurs to the extent of about 0.1 (dry weight) in an annual shrub, qinghao or (Artemisia annua), which grows in most provinces of China. Unfortunately, the world demand for qinghaosu far exceeds the supply, and there is considerable pressure to develop bioactive analogues, or to develop alternative sources for the compound. The compound has been prepared by total synthesis in the laboratory, but the structural complexity is such that no total laboratory synthesis has been economically feasible.